[llvm] 5367369 - [Support] Add file lock/unlock functions
Serge Pavlov via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 28 02:45:16 PDT 2020
Author: Serge Pavlov
Date: 2020-07-28T16:44:23+07:00
New Revision: 536736995bf5d073853c7e884968c9847b4ae64d
URL: https://github.com/llvm/llvm-project/commit/536736995bf5d073853c7e884968c9847b4ae64d
DIFF: https://github.com/llvm/llvm-project/commit/536736995bf5d073853c7e884968c9847b4ae64d.diff
LOG: [Support] Add file lock/unlock functions
This is recommit of f51bc4fb60fb, reverted in 8577595e03fa, because
the function `flock` is not available on Solaris. In this variant
`flock` was replaced with `fcntl`, which is a POSIX function.
New functions `lockFile`, `tryLockFile` and `unlockFile` implement
simple file locking. They lock or unlock entire file. This must be
enough to support simulataneous writes to log files in parallel builds.
Differential Revision: https://reviews.llvm.org/D78896
Added:
Modified:
llvm/include/llvm/Support/FileSystem.h
llvm/lib/Support/Unix/Path.inc
llvm/lib/Support/Windows/Path.inc
llvm/unittests/Support/ProgramTest.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Support/FileSystem.h b/llvm/include/llvm/Support/FileSystem.h
index a29a9d787947..b6d2a9f3aad5 100644
--- a/llvm/include/llvm/Support/FileSystem.h
+++ b/llvm/include/llvm/Support/FileSystem.h
@@ -1131,6 +1131,43 @@ Expected<file_t>
openNativeFileForRead(const Twine &Name, OpenFlags Flags = OF_None,
SmallVectorImpl<char> *RealPath = nullptr);
+/// Try to locks the file during the specified time.
+///
+/// This function implements advisory locking on entire file. If it returns
+/// <em>errc::success</em>, the file is locked by the calling process. Until the
+/// process unlocks the file by calling \a unlockFile, all attempts to lock the
+/// same file will fail/block. The process that locked the file may assume that
+/// none of other processes read or write this file, provided that all processes
+/// lock the file prior to accessing its content.
+///
+/// @param File The descriptor representing the file to lock.
+/// @param Timeout Time in milliseconds that the process should wait before
+/// reporting lock failure. Zero value means try to get lock only
+/// once.
+/// @returns errc::success if lock is successfully obtained,
+/// errc::no_lock_available if the file cannot be locked, or platform-specific
+/// error_code otherwise.
+///
+/// @note Care should be taken when using this function in a multithreaded
+/// context, as it may not prevent other threads in the same process from
+/// obtaining a lock on the same file, even if they are using a
diff erent file
+/// descriptor.
+std::error_code
+tryLockFile(int FD,
+ std::chrono::milliseconds Timeout = std::chrono::milliseconds(0));
+
+/// Lock the file.
+///
+/// This function acts as @ref tryLockFile but it waits infinitely.
+std::error_code lockFile(int FD);
+
+/// Unlock the file.
+///
+/// @param File The descriptor representing the file to unlock.
+/// @returns errc::success if lock is successfully released or platform-specific
+/// error_code otherwise.
+std::error_code unlockFile(int FD);
+
/// @brief Close the file object. This should be used instead of ::close for
/// portability. On error, the caller should assume the file is closed, as is
/// the case for Process::SafelyCloseFileDescriptor
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index d91b269cc6d3..fa4682dd33d2 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -33,6 +33,7 @@
#include <dirent.h>
#include <pwd.h>
+#include <sys/file.h>
#ifdef __APPLE__
#include <mach-o/dyld.h>
@@ -1078,6 +1079,50 @@ Expected<size_t> readNativeFileSlice(file_t FD, MutableArrayRef<char> Buf,
return NumRead;
}
+std::error_code tryLockFile(int FD, std::chrono::milliseconds Timeout) {
+ auto Start = std::chrono::steady_clock::now();
+ auto End = Start + Timeout;
+ do {
+ struct flock Lock;
+ memset(&Lock, 0, sizeof(Lock));
+ Lock.l_type = F_WRLCK;
+ Lock.l_whence = SEEK_SET;
+ Lock.l_start = 0;
+ Lock.l_len = 0;
+ if (::fcntl(FD, F_SETLK, &Lock) != -1)
+ return std::error_code();
+ int Error = errno;
+ if (Error != EACCES && Error != EAGAIN)
+ return std::error_code(Error, std::generic_category());
+ usleep(1000);
+ } while (std::chrono::steady_clock::now() < End);
+ return make_error_code(errc::no_lock_available);
+}
+
+std::error_code lockFile(int FD) {
+ struct flock Lock;
+ memset(&Lock, 0, sizeof(Lock));
+ Lock.l_type = F_WRLCK;
+ Lock.l_whence = SEEK_SET;
+ Lock.l_start = 0;
+ Lock.l_len = 0;
+ if (::fcntl(FD, F_SETLKW, &Lock) != -1)
+ return std::error_code();
+ int Error = errno;
+ return std::error_code(Error, std::generic_category());
+}
+
+std::error_code unlockFile(int FD) {
+ struct flock Lock;
+ Lock.l_type = F_UNLCK;
+ Lock.l_whence = SEEK_SET;
+ Lock.l_start = 0;
+ Lock.l_len = 0;
+ if (::fcntl(FD, F_SETLK, &Lock) != -1)
+ return std::error_code();
+ return std::error_code(errno, std::generic_category());
+}
+
std::error_code closeFile(file_t &F) {
file_t TmpF = F;
F = kInvalidFile;
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index e352beb77616..3570d1d6e056 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -1260,6 +1260,43 @@ Expected<size_t> readNativeFileSlice(file_t FileHandle,
return readNativeFileImpl(FileHandle, Buf, &Overlapped);
}
+std::error_code tryLockFile(int FD, std::chrono::milliseconds Timeout) {
+ DWORD Flags = LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY;
+ OVERLAPPED OV = {0};
+ file_t File = convertFDToNativeFile(FD);
+ auto Start = std::chrono::steady_clock::now();
+ auto End = Start + Timeout;
+ do {
+ if (::LockFileEx(File, Flags, 0, MAXDWORD, MAXDWORD, &OV))
+ return std::error_code();
+ DWORD Error = ::GetLastError();
+ if (Error == ERROR_LOCK_VIOLATION) {
+ ::Sleep(1);
+ continue;
+ }
+ return mapWindowsError(Error);
+ } while (std::chrono::steady_clock::now() < End);
+ return mapWindowsError(ERROR_LOCK_VIOLATION);
+}
+
+std::error_code lockFile(int FD) {
+ DWORD Flags = LOCKFILE_EXCLUSIVE_LOCK;
+ OVERLAPPED OV = {0};
+ file_t File = convertFDToNativeFile(FD);
+ if (::LockFileEx(File, Flags, 0, MAXDWORD, MAXDWORD, &OV))
+ return std::error_code();
+ DWORD Error = ::GetLastError();
+ return mapWindowsError(Error);
+}
+
+std::error_code unlockFile(int FD) {
+ OVERLAPPED OV = {0};
+ file_t File = convertFDToNativeFile(FD);
+ if (::UnlockFileEx(File, 0, MAXDWORD, MAXDWORD, &OV))
+ return std::error_code();
+ return mapWindowsError(::GetLastError());
+}
+
std::error_code closeFile(file_t &F) {
file_t TmpF = F;
F = kInvalidFile;
diff --git a/llvm/unittests/Support/ProgramTest.cpp b/llvm/unittests/Support/ProgramTest.cpp
index 9052b66b5fb9..84a5d3f64cfe 100644
--- a/llvm/unittests/Support/ProgramTest.cpp
+++ b/llvm/unittests/Support/ProgramTest.cpp
@@ -14,6 +14,7 @@
#include "llvm/Support/Path.h"
#include "gtest/gtest.h"
#include <stdlib.h>
+#include <thread>
#if defined(__APPLE__)
# include <crt_externs.h>
#elif !defined(_MSC_VER)
@@ -361,4 +362,57 @@ TEST_F(ProgramEnvTest, TestExecuteAndWaitStatistics) {
ASSERT_GE(ProcStat->TotalTime, ProcStat->UserTime);
}
+TEST_F(ProgramEnvTest, TestLockFile) {
+ using namespace llvm::sys;
+
+ if (const char *LockedFile = getenv("LLVM_PROGRAM_TEST_LOCKED_FILE")) {
+ // Child process.
+ int FD2;
+ ASSERT_NO_ERROR(fs::openFileForReadWrite(LockedFile, FD2,
+ fs::CD_OpenExisting, fs::OF_None));
+
+ std::error_code ErrC = fs::tryLockFile(FD2, std::chrono::seconds(5));
+ ASSERT_NO_ERROR(ErrC);
+ ASSERT_NO_ERROR(fs::unlockFile(FD2));
+ close(FD2);
+ exit(0);
+ }
+
+ // Create file that will be locked.
+ SmallString<64> LockedFile;
+ int FD1;
+ ASSERT_NO_ERROR(
+ fs::createTemporaryFile("TestLockFile", "temp", FD1, LockedFile));
+
+ std::string Executable =
+ sys::fs::getMainExecutable(TestMainArgv0, &ProgramTestStringArg1);
+ StringRef argv[] = {Executable, "--gtest_filter=ProgramEnvTest.TestLockFile"};
+
+ // Add LLVM_PROGRAM_TEST_LOCKED_FILE to the environment of the child.
+ std::string EnvVar = "LLVM_PROGRAM_TEST_LOCKED_FILE=";
+ EnvVar += LockedFile.str();
+ addEnvVar(EnvVar);
+
+ // Lock the file.
+ ASSERT_NO_ERROR(fs::tryLockFile(FD1));
+
+ std::string Error;
+ bool ExecutionFailed;
+ ProcessInfo PI2 = ExecuteNoWait(Executable, argv, getEnviron(), {}, 0, &Error,
+ &ExecutionFailed);
+ ASSERT_FALSE(ExecutionFailed) << Error;
+ ASSERT_TRUE(Error.empty());
+ ASSERT_NE(PI2.Pid, ProcessInfo::InvalidPid) << "Invalid process id";
+
+ // Wait some time to give the child process a chance to start.
+ std::this_thread::sleep_for(std::chrono::milliseconds(100));
+
+ ASSERT_NO_ERROR(fs::unlockFile(FD1));
+ ProcessInfo WaitResult = llvm::sys::Wait(PI2, 5 /* seconds */, true, &Error);
+ ASSERT_TRUE(Error.empty());
+ ASSERT_EQ(0, WaitResult.ReturnCode);
+ ASSERT_EQ(WaitResult.Pid, PI2.Pid);
+ sys::fs::remove(LockedFile);
+}
+
} // end anonymous namespace
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